Pacific leatherback turtles, the largest turtles on Earth, could go extinct within the next 20 years, a new study finds.

According the report, published in the journal Ecosphere, around 75 percent of Pacific leatherback turtles nest at Bird's Head Peninsula in Indonesia. Researchers estimate that only 489 breeding turtles remain on the largest nesting site in the Pacific. That's a 78 percent decline over the last 27 years.

There are two main causes for the decline: humans and warming beaches.

WikipediaThe turtles are small as babies, but can can grow to six feet long and weigh as much as 2,000 pounds.

Fisherman kill the turtles for meat. The eggs are also harvested for food. Dogs and pigs that roam the beaches also eat some of the eggs. Warmer sand, due to increasing temperatures, can kill the eggs, too.

“If the decline continues, within 20 years it will be difficult if not impossible for the leatherback to avoid extinction," Thane Wibbels, a biology professor at the University of Alabama said in a statement.